Rail transportation is generally recognized as being more economical than truck transportation for bulk commodities such as aggregates. Large quantities of such commodities can be moved by a small crew at low costs. However, rail transportation frequently loses out in competitive situations because of the cost of unloading, stockpiling, and delivering the commodity to the ultimate location. Rail transportation also loses out in competitive situations because of the difficulty in delivering the product to a desired location.
Even though large quantities of bulk material can be transported at low costs from one terminal to another, the burden is placed on the unloading facility to maintain the economics of this method of transportation for the purchaser of the commodity. Even if the unloading is slow, the train is therefore delayed for a substantial period of time for the unloading to be accomplished. There is an added investment cost per ton handled for the use of the railroad equipment. One problem, in this regard, is that rail transportation is a twenty-four (24) hour operation while many of the industries it serves operate only during daylight hours. Often, a train makes good speed from origin to destination, only to be delayed for several hours waiting to be unloaded. Each hour of delay adds to the transportation costs as much as an additional twenty-five (25) miles of haul.
As an example of the efficiency of rail transport for bulk commodities, a train with a two-man crew pulling 1600 net tons at 55 miles per hour would be producing 32 times as many ton-miles per hour as a dump truck driver hauling 25 tons at 55 miles per hour.
Another problem that has affected the efficiency of rail transportation for bulk commodities is that, under current methods, the quick unloading of a commodity train requires high capacity equipment and facilities which are idle most of the time. Such high-capacity equipment and facilities are expensive and add significantly to the investment costs per ton handled.
In the past, there have been many methods that have been used for the unloading of bulk materials from trains. For example, bottom dumping hopper cars are equipped with automatic doors that are opened automatically as the cars move over a pit, where the pit facility includes a feeder and a conveyor. Either a pit or an elevated trestle is required for this method, so that this method is ruled out at many locations. Obviously, the providing of a pit or trestle facility with associated conveyor systems is expensive. Another method involves the use of rotary car dumpers. These are commonly used for unloading coal and electric generating plants. Once again, the equipment for unloading the cars is highly specialized and expensive. Side dumping cars have been also used for many years. These side dumping cars, however, cannot be dumped on level ground. They require an elevated truck or a built-up embankment, for example, so that the dumped material will flow over the side of the embankment and not flow back over the track. In addition, backhoes or other loading equipment are used to unload standard gondola cars. These methods are generally slow, promoting the delay problems mentioned hereinabove.
A significant development in the unloading of hopper cars occurred with the invention of U.S. Pat. No. 4,925,356, issuing on May 15, 1990, to the present inventor and to William B. Snead. U.S. Pat. No. 4,925,356 disclosed a self-unloading train for the transfer of bulk commodities that comprises a plurality of hopper cars, a train conveyor, and a gating system. The plurality of hopper cars are coupled together to form a train. Each hopper car has at least one hopper having walls inclined at shallow angles to the vertical and a bottom discharge opening having a width at least 50% of the distance between the wheels of the hopper cars. The train conveyor is an endless belt supported on the cars and underlies each of the hopper discharge openings. This endless belt receives the material discharged from the hopper discharge openings. The train conveyor extends the length of the plurality of hopper cars. The train conveyor has a width that is substantially greater than the width of the discharge openings. The gating systems are operable selectively so as to discharge material from the hoppers onto the train conveyor. In particular, these gating systems are made up of clamshell-type gates that are pivotted about the axis parallel to the train conveyor. These clamshell-type gates assist in controlling the flow of material onto the train conveyor.
Each of the hopper cars of this invention has a center sill. The return run of the conveyor belt is supported by split return idlers disposed along each side of the center sill. The supply run of the conveyor belt is supported by catenary troughing idlers disposed immediately above the return run. A suitable drive system is provided for the train conveyor and the transfer conveyor. The drive system includes electric drive motors for the conveyor, a generator for providing electric power to the drive motors, and an internal combustion engine for driving the conveyor.
The actual embodiment of U.S. Pat. No. 4,925,356 has been very successful in actual operation. After extended use, it was found that this "DUMP TRAIN" should normally be unloaded on straight sections of track. Since the Dump Train has a substantial length, it was found that a limitation to the use of the Dump Train was that the Dump Train could not be unloaded on curved sections of track. If the train was unloaded on a curved section of track, then a great deal of deflection and distortion of the conveyor belt would occur. Any deflection or distortion of the conveyor belt could minimize the effectiveness of the Dump Train and could cause excessive wear and damage to the conveyor belt. In many areas of the country, and in many desired unloading locations, such long straight sections of track are not readily available. As such, a need developed for enabling the Dump Train to be unloaded on curved sections of track. This adds greatly to the effectiveness of the Dump Train concept, opens more markets for the use of the Dump Train, and allows the Dump Train to be increasingly flexible to the needs of the user.
In the past, there has not been great experimentation with conveyor belts for traversing curves. Except in the specialized application of the Dump Train, it is much simpler for conveyor designers to design straight sections of conveyor belts which discharge onto adjacent straight sections of conveyor belt. There has seldom been a need for designing a curved section of conveying equipment.
It is an object of the present invention to provide a self-unloading train t hat is suitable for discharging material from curved sections of track.
It is another object of the present invention to provide a conveyor guide system that resists deflection and distortion of the conveyor belt when operating on curves.
It is another object of the present invention to provide a training idler assembly that can be easily adapted for use on self-unloading trains.
It is still a further object of the present invention to provide a training idler assembly for a self-unloading train that is economical and easy to operate.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.